Strain insulator assembly



May 11, 1948. J. B. cooK STRAIN INSULATOR ASSEMBLY Flled March 31, 1945Q m NE Q Q kfofirz firown Cog/7c J; 4 3 m: JZ g Patented May 11, 1948STRAIN INSULATOR ASSEMBLY.

John Brown Cook, Chicago, Ill., assignor to Reliable Electric Company,Chicago, 111., a corporation of Illinois Application March 313545,Serial No. 585,917

My invention relates to strain insulators and particularly to aninsulating member for use in a splice having characteristics similar tothat shown in the patent to Fotsch 2,138,913, patented December 6, 1938.

The purpose of my invention is to provide an insulating member for thestrain insulator, that is made of molded insulating'material that isreinforced with insulating fibres so as to increase the strength thereofagainst shear and tensile stress. i

It is the further purpose of my invention to provide insulating membermade of a molded plastic reinforced with fibrous insulating members thatis molded so as to form a plurality of annular grooves therein whichreceive the corrugations provided in sleeve-like members that serve as ameans for connecting the ends of the conductors to the strain insulator.

It is the further purpose of my invention to provide an insulatingmember of the above referred to character in which the insulating fibrereinforcing members are causedto flow with the material in molding theannular grooves therein so that said reinforcing members are offset atThe body portion of the insulating member is made up of a plasticmaterial that is readily molded and can be made of a substantiallytransparent plastic material. The reinforcing fibres are preferablyglass fibres and these are preferably molded in the insulating plasticbody in the form of cords made up of such fibres running generallylongitudinally of said insulating member. The cords can be arranged insubstantial parallelism extending lengthwise of the insulating member inspaced relation, or the cords can be stranded into a loose rope, whichrope is imbedded in the insulating body. In either case the cords extendsubstantially longitudinally of the insulating member and are molded inthe plastic insulating material in such a manner as to be surroundedthereby so that the separate cords have said insulating materialsurrounding the same,

7 Claims. (01. 174 17s) whether the cords are separate from each otheror are made into the form of a looserope-like member.

Other objects and advantages of my invention will appear as thedescription of the drawings proceeds. I desire to have it understood,however, that I do not intend to limit myself to the particular detailsshown or described, except as defined in the claims.

In the drawings:

Fig. 1 is a view partly in longitudinal section and partly in elevationthrough my improved strain insulator.

Fig. 2 is a section thereof taken on the line 2-2 of Fig. 1; and

Fig. 3 is a perspective view of a modified form of reinforcement used inmy insulating body.

Referring in detail to the drawings, my improved strain insulatorcomprises the sleeve-like members 5 which have gripping jaws 6 and ltherein, cooperating to secure the cdnductors 8 and 9 within saidsleeve-like members against longitudinal movement relative thereto, saidjaws being held in gripping engagement with said conductors by means ofa coil compression spring 10, in a similar manner to that shown in theabove referred to patent to Fotsch 2,138,913.

Said sleeve-like members 5 and 6 taper lengthwise and are provided withsubstantially cylindrical end portions H at the larger ends thereoffacing each other which are provided with a plurality of circumferentialcorrugations l2 therein providing inwardly directed annular ribs withinthe socket portions formed by said substantially cylindrical portions Halso serving as housing means for the springs l0.

Cooperating with said sockets with the inwardly directed annular ribstherein is an in sulating member 13 which is made up of a .body ofmolded insulating material which can be made of any insulating plasticthat has sufficient tensile strength, although transparent plasticmaterial has been found to be the preferred material up to the presenttime. The insulating member I3 is molded prior to assembly with thesleeve-like members in a generally cylindrical shape with a plurality ofannular grooves l4 therein arranged in spaced relation and conforming inspacing arrangement to the ribs formed by the corrugations 12. which areformed in the sleeve-like members after assembly of said insulatingmember therewith by spinning or otherwise, to thus provide an interlockbetween the metal sleeves 5 and the insulating body l3. Fibrousreinforcing means is provided for the insulating body I3, said fibrousreinforcement being of insulating material, glass fibres having beenfound to be particularly useful due to their tensile strength for thispurpose.- While separate glass fibres can be used to increase thetensile strength of the molded plastic insulating body, it has beenfound preferable to use cords made up of glass fibres. said glass fibrecords I! being arranged generally lengthwise of the body portion asshown in Figs. 1 and 2 of the drawings and being laid substantially inparallelism in the plastic material prior to the molding of the groovesH therein.

When the grooves I are molded in the plastic body it, the cords of glassfibres are caused to flow with the material so as to be deformed,providing indentations l 8 in said cords, which anchor the cords inposition and interlock certain of said cords with the inwardly directedannular ribs formed by the corrugations l2. Said cords extend from oneend I! to the other end ll of the insulating body ll. The deformation ofthe glass fibre members puts the cords, as well as the molded plasticmaterial forming the body in which said cords are imbedded, under acompression stress when the strain insulator is put under tension in usebetween the ends I! thereof and the rib formed by the corrugation i2nearest the mouth or open end I9 of each of the socket portions of thesleeves 5.

Between said innermost ribs in said sockets the strain insulator isunder tension in use but the reinforcing insulating fibres take up thistension strain, thus increasing greatly the strength of the insulatorover a molded body having no such reinforcing fibres against a tensionstress.

Instead of making the reinforcement of separate cords i5 extending insubstantial parallelism to each other, the cords Hi can be looselystranded into a rope indicated generally in Fig. 3 by the numeral 20,and this rope-like member of cords of insulating glass fibres is moldedin a body of insulatin material I! in the same manner as the separatefibres shown in Figs. 1 and 2 are molded therein, the plastic insulatingmaterial flowing between the cords that make up the rope-like member. Inboth forms of the invention, said plastic material molds itself in closeadjacency to the fibres that make up the cords as will be evident fromFig. 1, filling any recesses between the adjacent fibres to thus providea strong interlock between the plastic body in which said glass fibresare molded and the reinforcing members.

A strain insulator is thus provided which has an insulating body portionwhich has great tensile strength, the shear stress portion at each endof which is under compression in use instead of under tension and whichhas all the electrical insulating qualities that are required of astrain insulator of this character. Obviously the member l3 can be madeof desired length and cross-section with the metallic sleevelike membersspaced a desired distance apart at their proximate ends i9 so as toprovide the proper insulating gap there-between, and other suitablecooperating deformations than the annular grooves l4 and corrugations IIcan be provided for securing the insulating body to the metallicsleeves, as long as the glass fibres are embedded in the plastic bodyand said fibres are deformed or oflset at the securing portion of saidinsulating body to provide an interlock between said fibres and theholding formations on the sleeves.

Having thus described my invention, what I 4claimisnewanddesiretosecurebylatten Patcntis:

1. In a strain insulator an elongated smooth surfaced body of moldedinsulating material having a plurality of annular grooves around thesame and having a longitudinal reinforcement of a loosely stranded ropeof non-absorbent insulating fibre cords of greater tensile strength thansaid molded material molded therein to surround said cords with saidinsulating material, said rope beingdeformed at said grooves.

2. In a strain insulator an elongated body of molded insulating materialhaving a, plurality of annular grooves around the same at each endthereof and having a longitudinal reinforcement of spaced glass fibrecords molded therein. said cords being each surrounded by said moldedmaterial and being deformed at said grooves.

3. In a strain insulator an elongated smooth surfaced, imperforate,non-absorbent body of molded insulating material having a plurality ofannular grooves around the same at each end thereof and having alongitudinal reinforcement of a loosely stranded rope of glass fibrecords molded therein, said rope being deformed at said grooves and eachof said cords being surrounded by said molded material.

4. In a strain insulator an elongated smooth surfaced imperforateinsulating body portion having a plurality of alternating annulargrooves and ribs extending around the same formed therein adjacent theopposed ends thereof, said body portion comprising a mass of insulatingmaterial having a longitudinal reinforcement of flexible insulatingmaterial of greater tensile strength than said mass embedded therein andunited therewith, said reinforcement comprising fibrous membersextending substantially longitudinally of said body portion fromadjacent one end thereof to adjacent the other end thereof and saidreinforcement being deformed at said grooves to provide undulationstherein aligning with said grooves providing anchoring means for saidreinforcement adjacent the ends of said body portion.

5. In a strain insulator, an elongated smooth surfaced non-absorbentinsulating body portion, metallic sleeves having socket portionsreceiving the ends of said insulating body portion and spaced to providean insulating gap bridged only by said insulating body portion, saidsocket portions having circumferential corrugations therein and saidbody portion having formations therein adjacent its ends complementaryto said corrugations, said insulating body portion being composed of aplastic insulating material and insulating fibres of greater tensilestrength than said plastic material extending lengthwise of said bodyportion and enclosed within and united with said plastic material toprovide a longitudinal strain resisting reinforcement across said gap,said reinforcement being deformed at said corrugation receivingformations t interlock said corrugations therewith.

6. In a strain insulator, an elongated smooth surfaced non-absorbentinsulating body portion. metallic sleeves having socket portionsreceiving the ends of said insulating body portion and spaced to providean insulating gap bridged only by said insulating body portion, saidsocket portions having circumferential corrugations therein and saidbody portion havin formations therein adiacent its ends complementary tosaid corrugations. said insulating body portion being composed of aplastic insulating material and glass fibres extending lengthwise orsaid body portion and enclosed within and united with said plasticmaterial to provide a longitudinal strain resisting reinforcement acrosssaid gap, said reiniorcement being deformed at said corrugationreceiving formations to interlock said corrugations therewith.

7. In a strain insulator, an elongated smooth surfaced non-absorbentinsulating body portion, metallic sleeves having socket portionsreceiving the ends of said insulating body portion and spaced to providean insulating gap bridged only by said insulating body portion, saidsocket portions having circumferential corrugations therein and saidbody portion having formations therein adjacent its ends complementaryto said corrugations, said insulating body portion being composed of aplastic insulating material and corded glass fibres extending lengthwiseof said body portion and enclosed within and united go with said plasticmaterial to provide a longitudinal strain resisting reinforcement acrosssaid gap, said reinforcement being deformed at said corrugationreceiving formations to interlock said corrugations therewith.

JOHN BROWN COOK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS 10 Number Name Date 1,006,040 Alsberg Oct.. 17,1911 1,006,042 Alsberg Oct. 17, 1911 1,167,125 Sloper Jan. 4, 19161,373,576 Thomas Apr. 5, 1921 1,691,005 Burke Nov. 6, 1928 1,782,790Miller et a1 Nov. 25, 1930 2,014,441 Matthews Sept. 17, 1935 2,202,820Baird et al. June 4, 1940 FOREIGN PATENTS Number Country Date 216,527Switzerland Dec. 1, 1941 551,166 Great Britain Feb. 10, 1943

